Developer · Free Tool
Number Base Converter
Convert numbers between Binary, Octal, Decimal, and Hexadecimal instantly, with all four bases shown at once.
Binary = base 2 · Octal = base 8 · Decimal = base 10 · Hexadecimal = base 16
About this tool
Type a number into any one of the four fields (Binary, Octal, Decimal, or Hexadecimal) and the other three update instantly, so you always see all four representations of the same value side by side. Invalid digits for the selected base (like an 8 in a binary field) are flagged immediately.
Base conversion comes up constantly in low-level programming, networking, and debugging: reading a hex color or memory address, decoding octal file permissions, or checking what a binary flag field actually represents in decimal. This tool skips the mental math and shows the full picture at once.
Common uses
- Convert a hexadecimal color, memory address, or error code to decimal to reason about its actual value
- Decode Unix file-permission octal values (like 0755) into what they actually allow
- Check a binary bitmask or flags field against its decimal or hex equivalent while debugging
Frequently asked questions
Why does decimal 255 equal hexadecimal FF?
Hexadecimal is base 16, using digits 0-9 and A-F. FF means 15×16 + 15 = 255, the largest two-digit hex value, which is why it shows up constantly as a maximum (like 255 for a color channel or an 8-bit byte).
What are octal file permissions like 0755 actually encoding?
Each octal digit (base 8, digits 0-7) represents three permission bits (read, write, execute) for owner, group, and others respectively. 0755 decodes to rwxr-xr-x: the owner gets full access, everyone else gets read and execute only.
Is there a limit to how large a number this handles?
The tool uses JavaScript's BigInt internally, so it comfortably handles very large integers beyond the normal 53-bit safe integer limit, useful for 64-bit values that show up in low-level programming.
Is my data uploaded to a server?
No. This tool runs entirely in your browser using JavaScript, so nothing you type is transmitted, logged, or stored anywhere. You can even use it offline once the page has loaded.